Method of fusion joining



1952 J. WEIR ET AL METHOD OF FUSION JOINING Filed May 18,. 1948 IN V EN T 0RS Jizmes War HTTORNEY Patented May 27, 1952 cane-o smres @PATi-EZNT OFFl-iC-E Ohio, assignors to Aluminum Company of America, Pittsburgh, Pa., a corporation of iennsylmnia Appiication'May '18, 1948,, Sefi'zilNmZ'ZJWB 7 3 Claims. '1

This invention relates in genera-Ito a method of fusion joining metallic'parts. It is more particularly directed to Jfurnace brazing aluminous parts wherein at least one part is of varying'width or thickness adjacent that portion which enters into and forms an integral portion of a finished fusionjoint.

Fusionjoining has reached a high state of development, and in the light metal field, represented by aluminum and its alloys, it is now possible to replace many of the ferrous and other metals and alloys in structures which heretofore offered considerable manufacturing diificulties. There are, however, many designs and structures, regardless of the metal or alloy from which they may be produced, that do not lend themselves to known and practiced methods and procedure of fusion joining or brazing. This is particularly notice-d in structures wherein the strength of the joints does not come up to that required in a particular service. For example, in the construction of pump and turbine units of the centrifugal type, wherein intricately shaped vanes or blades of varying widths and thickness are employed,it has been considered a structural necessity to'fabricate suchunits by casting the blades as an integral portion of their housings to insure against failure of the units under operating conditions. Automotive and industrial torque converters .are examples of such units which are being manufactured byc'ast in methods.

W e have discovered a'fusion brazing or joining method-and technique, which has met with success in the commercial production of centrifugal type pumps and turbines, and in which the developed strength of the fusion joints between housings and vanes, in aluminum alloys, is equal to, and in many instances higher than integrally cast units of similar designby-selecting and employing wrought or forged and cast aluminum base alloy elements that respond to thermal treatments to increase the over-all strength of a fusion joined a'ssemblyincorporating the same. The invention is not confinedto aluminous materiais, however, since the method to be hereinafter described in detail, is applicable 'to other metals and -alloys that respond to fusion joining.

It is a general object of the invention 'to provide 'amethod of 'fusi'on'joining 'me'taliparts'whi'c'h ness immediately adjacent a surface forming an integral portion "of "such joints.

Another object of the invention is to pr vide a method of fusion "joining metallic parts inwhi'c'h '2 the 'zone of fjointure between the parts is generally sloping or curvilinear, as viewed in a vertical plane through such 'i'oints.

Other objects and advantages "will present themselves to those skilled "in this art on consideration .of the following description and appended claims, when read "in conjunction with the drawing, 'in'which:

Fig. 1 represents a plan view of elements or parts of "a "joint in assembled relationship prior to fusion joining;

Fig. '2 represents a sectional elevation taken along the 'line'II-TIoi Fig. '1;

:Fig. '3 represents :a sectional elevation taken along "the line IIIIII of Fig. 2 following a fusion joining operation;

Fig. 4 represents an elevational view of a turbine or pump vane;

Fig. .5 represents a'view of the upper face of the vane in Fig. 4";

Fig. 6 represents a bottom plan view of the vane IinFig. 4,;

.Fig. 7 represents a fragmentary assembly View of the vane in Fig. "4 in relation to housing memhers prior to Ifusion joining; :and

-Fig. .8 represents a sectional elevation taken along the line VIII-VIII of Fig. 7 following a fusion joining operation.

Referring to the drawing, and particularly 1 through 3, an assembly "is illustrated comprising a metal plate or base member ID above which is mounted a'wedge-shap'ed metalmember I2. The member l2, in 'accordancewith the practice of the invention, is supported in bearing contact at its thin or pointed end on the base member it, and .is otherwise progressively spaced therefrom towards its thickened end. This particular spac 'ing of members 1'0 and I2 is readily accomplished through the use of a suitable jig or fixture. In accordance with a "feature of the invention the members 10 and I 2 are'positioned in such a manner that the clearance increases progressively from an elevated point towards a point of lower elevation in the zone of jointure, as viewed from the thin towards the thick end of member 52.

In fusion joining "the members 16 and it, a fusible 'joiningmetal or alloy 14, in the form of a hairpin or .bent'wire, is positioned adjacent the thin end of member l2, as -by encompassing the end and portions of the surfaces defining the thin end of the member. The joining metal or jall'oy il'l is fselected'inireference to the metals or alloys "being joined and a suitable flux is used, if required, adiac'entthe surfaces of members it and I 2 in the "immediate area of the finished joint.

Heat is thereafter applied in sufficient amount to melt the joining material or alloy 14 which, through gravitational flow and capillary attraction, distributes itself along the edges of the joint and fills the intervening space between the juxtaposed surfaces of members It and I2. Proper selection of materials and temperature control will insure high strength jointure of the elements, furnace brazing technique, wherein the entire assembly is heated to a uniform temperature sufficient to melt the fusible material It, having been found satisfactory for this purpose.

In the preferred practice of the invention the volume of metal represented by the hairpin M is selected in sufficient amount to provide a continuous fillet around the lower edges of member 12, as well as fill the space under the bottom surface of member 12, shown to advantage in Fig. 3. It will also be understood that diffusion of the molten wire M into the metals or alloys constituting the members and I2 will take place in the formation of the fusion joint therebetween.

Figs. 4 through 8 illustrate a specific example of a commercial application of the invention in the manufacture of furnace brazed aluminum alloy turbine units for torque converters. Herein turbine or pump vanes or blades [5 previously made to exact shape (Figs. 4 through 6) in aluminum alloy, as by casting the same, are assembled within top and bottom housing members it and I8, respectively. As shown in Fig. '7, the vane I5 is spaced from its complementary housing member 18 by means of an aluminum washer 2t surrounding an aluminum alloy dowel or positioning stud or pin 22. The stud or pin 22 is preferably threaded into the bottom surface of the vane i5 and projects into a clearance hole or aperture in the housing [8. Also, it is preferred to use a second positioning stud or pin 24 mounted in the same manner, and for the same purpose as member 22. It is not essential that the studs or pins 22 and 24 be threaded elements, or that they be in threaded engagement with the underside of the vane 15. They may be loose pins or may be secured in either the vane l5 or housing member l8, their chief purpose being to insure proper relative positioning between their adjacent associated elements.

The vane is positioned within the housing H3 in contact therewith adjacent its two extreme ends, and is otherwise spaced therefrom over its curvilinear zone of jointure: therewith. The spacing of the blade or vane 15, in respect to its housing member is, progressively increases from its highest point of contact, defined by a narrow width of the vane, as at 25, towards an increased width of the vane l5, as at 25, at some lower level in the curvilinear plane or zone of juncture between the parts.

It is also to be observed that the extreme lower end 28 of the vane i5 is in contact with the housing it. This latter contacting relationship is primarily for purposes of assisting in the support of the vane and does not introduce any departure from the invention.

Ihe upper or top housing member is preferably prefabricated from a composite aluminum alloy brazing sheet, which has on its surface in contact with the vane 15 an integral aluminum-silicon brazing alloy coating 39.

With the various parts described above, assembled as illustrated in Fig. 7, an aluminum alloy brazing wire 32, bent to substantially hairpin shape, is placed in engagement with the vane 35 at its upper end 25. 1=he complete turbine unit, only a fragmentary section of which is illustrated at Fig. 7, includes a plurality of vanes l5, all of which are mounted in the same manner within the housing (8, which is preferably in the form of a forged or cast aluminum alloy, diskshaped member. Similarly, the member I6 is substantially U-shaped and is preferably drawn from a duplex brazing alloy sheet product.

In practice, the surfaces entering into the joints are suitably fluxed, the members assembled as illustrated in Fig. 7, and the entire assembly subjected to a furnace temperature suificient to melt the hairpin brazing wires 32 and cause the same to gravitationally flow and react to capillary attraction to provide filleted jointure around the base of each vane :5, as well as fill up the intervening space between the underside of each vane and the housing member l8 (Fig. 8). The upper joint between each vane [-5 and channel member [6 is formed in the manner described in United States patents to Gustav O. I-Ioglund 2,258,681 and 2,312,039, issued October 14, 1941, and February 23, 1943, respectively. As in the description of the fusion joint illustrated in Figs. 1 through 3, selection of the aluminum alloys, flux, brazing wire and brazing temperature are essential to produce maximum strength characteristics in the final fusion joined assembly. Known thermal treatments may be used to develop high strength properties in the finished articles. Also the volume of brazing metal in each of the wires 32 should be such that the desired size of fillet for definite strength requirements is produced, the clearance under the vanes being selected and controlled to provide any desired size of fillet, and location of the same.

What is claimed is:

1. A method of making a joint between metallic members, wherein the zone of jointure is defined by a member of varying section width juxtaposed above the member to which it is to be joined, the steps comprising, assemblying the first-mentioned member above and in contact with the second-mentioned member at a point defined by a narrow width of the first-mentioned member, adjusting said members to position a wider width of the first-mentioned member at a lower elevation than the point of contact between said members, progressively separating the members from the point of contact towards the wider section. providing a fusible joining material adjacent the point of contact, and raising the temperature of the fusible joining material to melt the same, whereby the melt under gravitational and capillary attraction distributes itself over the zone of jointure to completely fill the intervening space between the members and provide filleted jointure therebetween.

2. A method of fusion joining metallic parts in which the zone of jointure therebetween lies in a sloping plane, and in which at least one part to be joined varies in width adjacent the zone of jointure, the steps comprising, positioning the parts in juxtaposed relationship, providing contact between the parts at a point in the part of varying width defined by increasing width in said part beyond said point of contact, said point of contact being higher in elevation than the immediately adjacent points in the sloping zone of jointure, progressively separating the parts along the sloping zone of jointure from the point of contact towards a wider section of the part of varying width, providing a fusible joining material adjacent the point of contact, and raising the temperature of the fusible joining material to melt the same, whereby the melt through gravitational flow and capillary attraction distributes itself over the sloping zone of jointure to completely fill the intervening space between the parts and provide filleted jointure therebetween.

3. A method of joining metallic parts in which the zone of jointure therebetween is curvilinear in form, and in which at least one of said parts varies in width adjacent the zone of jointure, the steps comprising, positioning the parts in juxtaposed relationship, providing contact between the parts at a point in the part of varying width defined by increasing width in said part beyond said point, said point of contact being higher in elevation than the immediately adjacent points in the curvilinear jointure zone, progressively separating the parts along the curvilinear zone of jointure from the above defined point of contact towards a wider section of the part of varying width, providing a fusible joining material adjacent the point of contact in amount sufiicient to fill the intervening space between the parts and provide filleted jointure therebetween, and raising the temperature of the assembled parts to melt the fusible joining material, whereby the melt through gravitational flow and capillary attraction distributes itself over the curvilinear zone of jointure to completely fill the space between the parts and provide a filleted joint.

JAMES WEIR. CHARLES H. DULIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Page 7 of Bulletin No. 12-A titled Sil-Fos and Easy-Flo. Copyrighted in 1943 by Handy and Harman, 82 Fulton St, New York, N. Y. 

